Rocket engine thrust chamber assembly

ABSTRACT

A thrust chamber assembly for liquid fueled rocket engines and the method of making it wherein a two-piece mandrel having the configuration of an assembly having a combustion chamber portion connected to a nozzle portion through a throat portion is wrapped with a silica tape saturated with a phenolic resin, the tape extending along the mandrel and covering the combustion chamber portion of the mandrel to the throat portion. The width of the tape is positioned at an angle of 30 to 50° to the axis of the mandrel such that one edge of the tape contacts the mandrel while the other edge is spaced from the mandrel. The phenolic in the tape is cured and the end of the wrap is machined to provide a frustoconical surface extending at an angle of 15 to 30° with respect to the axis of the mandrel for starting a second wrap on the mandrel to cover the throat portion. The remainder of the mandrel is wrapped with a third silica tape having its width positioned at a angle of 5 to 20° from the axis of the mandrel. The resin in the third tape is cured and the assembly is machined to provide a smooth outer surface. The entire assembly is then wrapped with a tow of graphite fibers wetted with an epoxy resin and, after the epoxy resin is cured, the graphite is machined to final dimensions.

ORIGIN OF THE INVENTION

[0001] This invention was made by employees of the United StatesGovernment and may be manufactured and used by or for the Government forgovernmental purposes without the payment of any royalties.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to thrust chamber assemblies for rocketengines.

[0004] 2. Prior Art

[0005] It is known to use ablative liners for rocket engine combustionchambers. U.S. Pat. No. 4,458,595 discloses a solid rocket motor havinga layer of silicone rubber and a second layer of an ablative liningplaced between the motor casing and the propellant grain. The ablativelining layer contains chopped novoloid fibers 14 microns in diameter andhaving a nominal length of 1 millimeter interspersed throughout thepolymeric composition.

[0006] U.S. Pat. No. 5,352,312 discloses a rocket motor insulation madeof a liquid crystal polymer such as a wholly aromatic polyester withfillers such as glass or carbon fibers.

[0007] U.S. Pat. No. 3,973,397 discloses a rocket motor with an ablativelining made of a terpolymer of ethylene, propylene and a nonconjugateddiene and inert fillers such as heavy metal halides, calcium hydroxideand magnesium hydroxide.

SUMMARY OF THE INVENTION

[0008] A thrust chamber assembly for liquid fueled rocket engines andthe method of making it wherein a two-piece mandrel having theconfiguration of an assembly having a combustion chamber portionconnected to a nozzle portion through a throat portion is wrapped with asilica tape saturated with a phenolic resin, the tape extending alongthe mandrel and covering the combustion chamber portion of the mandrelto the throat portion. The width of the tape is positioned at an angleof 30 to 50° to the axis of the mandrel such that one edge of the tapecontacts the mandrel while the other edge is spaced from the mandrel.The phenolic in the tape is cured and the end of the wrap is machined toprovide a frustoconical surface extending at an angle of 15 to 30° withrespect to the axis of the mandrel for starting a second wrap on themandrel to cover the throat portion. The remainder of the mandrel iswrapped with a third silica tape having its width positioned at a angleof 5 to 20° from the axis of the mandrel. The resin in the third tape iscured and the assembly is machined to provide a smooth outer surface.The entire assembly is then wrapped with a tow of graphite fibers wettedwith an epoxy resin and, after the epoxy resin is cured, the graphite ismachined to final dimensions.

DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a schematic side view of a two-piece mandrel showingstructure used with the mandrel to support graphite fibers wrapped onthe mandrel to provide structural support.

[0010]FIG. 2A is a greatly enlarged fragmentary view of the combustionchamber portion of the mandrel wrapped with a silica tape saturated witha phenolic resin.

[0011]FIG. 2B is the view of FIG. 2A after the end of the first wrap hasbeen machined to provide a starting surface or ramp for the second wrapof silica tape.

[0012]FIG. 2C is the view of FIG. 2B after the second wrap covering thethroat portion has been completed.

[0013]FIG. 2D is the view of FIG. 2C after the third wrap has beencompleted.

[0014]FIG. 3 is the view of FIG. 2 after the mandrel has been completelywrapped with the silica tape and the tow of graphite fibers and thecured overwrap of graphite fibers has been severed, fore and aft.

[0015]FIG. 3A is an enlarged fragmentary view showing the completedforward end of the thrust chamber showing a ring bonded between thesilica phenolic wraps and the graphite wraps for supporting an injector.

[0016]FIG. 4 is a cross sectional view showing the manner in which themandrel is constructed.

[0017]FIG. 5 is a cross sectional view showing the completed thrustchamber with support rings attached.

DETAILED DESCRIPTION OF THE INVENTION

[0018] Referring now in detail to the drawings, there is shown in FIGS.1 and 4 a two-piece mandrel having a combustion chamber portion 12connected to a nozzle portion 13 through a throat portion 14, theseportions having the configuration of the inner surface of the thrustchamber assembly to be made by this process—a generally hourglassconfiguration. The mandrel is made in two pieces 19 and 20 (FIG. 4) suchthat it can be taken apart and withdrawn from the completed thrustchamber assembly.

[0019]FIG. 2A shows the first step in the making of this thrust chamberassembly. A ring 24 extending around the end of the combustion chamberportion 12 of the mandrel is provided with a surface 25 which isinclined at an angle of 30 to 50°, preferably 40 to 45°, with respect tothe axis 26 of the mandrel. The surface 25 provides a starting point forthe wrapping of a first silica tape 30 saturated with a phenolic resin,such that the width of the tape is positioned at the same angle withrespect to the axis 26. The actual positioning of the tape is shown inFIGS. 2A-3. With the tape 30 wrapped in this manner one edge of the tapeis in contact with the mandrel such that, when the combustion chamberportion is used as a combustion chamber the layers of the wrapped tapecannot delaminate.

[0020] Silica tape is commercially available. The tape is woven fromfiberglass fibers and then treated with nitric acid. The nitric acidleaches out the sodium and lithium to leave a silica fabric The fabricis cut on the bias, at 45°, to form strips (not shown) having a widthgenerally the same as the that desired for the tapes. The ends of thestrips are then sewed together to form long lengths of the tape. When atape of his type is used, the inner edge of the tape is free to compressand the outer edge is free to stretch. This allows the tape to be woundas described herein. The tape is saturated with a phenolic resin priorto being wrapped. The angles described herein are the angles between aline formed by the intersection of the tape with a plane in which theaxis of the assembly is lying.

[0021] The first tape is wrapped from the combustion chamber portion tothe throat portion 14 and terminates in an end 31. The phenolic resin inthe wrapped silica tape is cured and the end 31 of the wrap is machinedto a line 34 (FIG. 2A) to provide a starting point for the wrapping ofthe second silica tape 35. This machining provides a frustoconicalsurface (line 34)) which is the starting point for wrapping the secondtape 35, the width of this surface being positioned at an angle of 15 to30°, preferably 15 to 25°, to the axis 26 of the mandrel. The secondtape 35 is wrapped on the throat portion 14 of the mandrel at this angleuntil the end of the throat portion 14 is reached.

[0022] The resin in the second tape is then cured and the end of thesecond portion is machined to a line 37 (FIG. 2C) to give a startingsurface for the third wrap of silica tape 41 (FIG. 2D). This third wrap41 is positioned at an angle of 5 to 15°, preferably 8 to 12°, to theaxis of the mandrel and is carried to the end of the nozzle portion 12.The third wrap is then cured and the first wrap is cut off along line 45of FIG. 3 and then the assembly is machined to provide a smooth outersurface and to provide a surface 42.

[0023]FIG. 1 shows the last wrapping step. A tow 47 of graphitefilaments is wetted with an epoxy resin and then wrapped as shown inFIG. 1, the mandrel being mounted on a shaft 48 (FIGS. 1 and 4) which isdriven slowly by a motor 49. One end of the mandrel is fitted with adome 52 carrying a row of pins 53 extending around the dome. The purposeof the pins 53 is to hold the filaments making up the tow 47 in place asthe tow is wrapped around the dome.

[0024] The other end of the mandrel is fitted with a pair of concentricrings 57 and 58 positioned as shown in FIG. 1, the rings being supportedby posts 61 and 62, respectively. The rings 57 and 58 carry a pluralityof pins 65 and 66, respectively. The purpose of the pins 65 and 66 is tohold the filaments in the tow 47 in alignment as the tow is wound overthe rings for the next pass over the mandrel. From FIG. 1 it can be seenthat when the mandrel is completely covered by the tow 47, the wrappedtow will exhibit a diamond pattern.

[0025] After the graphite tow wrapping is completed, the epoxy resin iscured and the graphite layer is severed along lines 70 and 71. The outersurface of the graphite layer is then machined to a smooth surface. Thetwo piece mandrel is then removed from the thrust chamber assembly andan injector (not shown) is attached to the upper end of the thrustchamber assembly. Such an injector is disclosed and claimed inapplication Ser. No. 09/168,341, filed: Oct. 5, 1998 in the names ofCharles A. Cornelius, et al. for LOW COST INJECTOR ASSEMBLY.

[0026] Prior to use of the use of the thrust chamber assembly, a pair ofattachment rings 74 and 75 (FIG. 5) are bonded to the assembly. Theseattachment rings are using for supporting other equipment (not shown)which cooperates with the assembly and gimbals the entire assembly forsteering a rocket (not shown) on which the assembly is mounted

[0027] In operation, the injector (not shown) injects streams ofkerosene and liquid oxygen into the combustion chamber where thekerosene is burned to provide thrust for the engine. A char layer formson the silica phenolic tape layer, providing insulation for theassembly. The angle at which the silica layers are wrapped prevents thetape layers from delaminating.

What is claimed is:
 1. The method for making a thrust chamber assemblyfor a rocket engine, said assembly having a combustion chamber a throatand a nozzle connected in series, comprising a. providing a two-piecemandrel having a configuration of said combustion chamber, throat andnozzle portions portion, said mandrel having an axis; b. wrapping themandrel with a generally flat fabric tape saturated with a curablethermosetting resin; said tape having first and second edges, said tapewidth being positioned at an acute angle with respect to said axis suchthat one of the edges of the tape is in contact with the mandrel and theother edge is spaced from the mandrel; c. curing the thermosettingresin; d. wrapping the assembly with a tow of graphite fibers wettedwith an epoxy resin to form a structural layer; and e. curing the epoxyresin.
 2. The process of claim 1 wherein the tape is a silica tape. 3.The process of claim 2 wherein the tape is saturated with phenolicresin.
 4. The method for making a thrust chamber assembly for a rocketengine, said assembly having a combustion chamber, a throat and a nozzleconnected in series, comprising: a. providing a two-piece mandrel havinga configuration of said combustion chamber, throat and nozzle portionsportion, said mandrel having an axis; b. wrapping said combustionchamber and said throat portions of the mandrel with a first fabric tapesaturated with a curable, thermosetting resin, said wrapping having anend at said throat portion of said mandrel; said tape being wrapped atan angle such that the width of the tape is positioned at an angle of 30to 50° with respect to said axis; c. curing the thermosetting resin; d.machining the end of the wrapping to form a frustoconical surface havingan angle of 5 to 30° with respect to said axis; e. wrapping the nozzleportion with a second fabric tape saturated with a curable,thermosetting resin, said wrapping beginning at said frustoconicalsurface and having the same angle as said frustoconical surface; f.curing the second fabric tape; g. machining said end of said second tapeto form a third frustoconical surface having angle of 5 to 15° withrespect to said axis; h. wrapping a third fabric tape saturated with athermosetting resin, said third wrapping beginning at the machined endof said second wrap and having the same angle as the third frustoconicalsurface; i. curing the third fabric tape; j. wrapping the assembly witha tow of graphite fibers wetted with an epoxy resin to form a structurallayer; and k. curing the epoxy resin.
 5. The process of claim 4 whereinthe fabric tape is a tape woven from silica fibers.
 6. The process ofclaim 5 wherein the thermosetting resin is a phenolic resin.
 7. Theprocess of claim 6 wherein the first fabric tape is wrapped at an angleof 40 to 45° with respect to said axis; the second fabric tape iswrapped at an angle of 15 to 25° with respect to said axis; and thethird fabric tape is wrapped at an angle of 8 to 12° with respect tosaid axis.
 8. A thrust assembly for a rocket engine having an axis and agenerally hourglass configuration made up of a combustion chamberportion connected through a throat portion to a nozzle portion,comprising a. a layer of fabric tape wrapped in a helical wrap to formsaid portions, said tape having first and second edges, the width ofsaid tape being positioned at an acute angle with respect to said axissuch that one edge of the tape forms the inner surface of the wrappedtape and the other edge forms the outer surface of said wrapped tape,said tape being embedded in a cured thermosetting resin, and b. a layerof graphite fibers wrapped around the wrapped fabric tape to form astructural layer, said graphite fibers being embedded in a cured epoxyresin.
 9. The structure of claim 8 wherein the fabric tape is wrapped atangle of 30 to 50° on said combustion chamber portion, at an angle of 5to 30° on said throat portion and at an angle of 5 to 15° on said nozzleportion.